1. Field of the Invention
The present invention relates to a dispensing head for a container holding a product of liquid-to-pasty consistency, especially a cosmetic or pharmaceutical product.
2. Description of the Related Art
U.S. Pat. No. 4,099,651 describes a dispensing head comprising a tubular element fixed to the neck of a flexible tube. The tubular element has, over at least part of its length, a plane partition which extends beyond the tubular element so as to define two output channels for the product. A sleeve made of elastic material is slipped over the tubular element and over that part of the plane partition which extends beyond it. The closure system consists of the edge of the sleeve of elastic material which rests on the two opposite faces of the end of the plane partition. This edge is in contact with the partition when no product is being dispensed and moves away from the partition under the pressure of the product. Because of its elasticity, the edge comes back into contact with the faces when the dispensing operation stops.
In such a closure system, the contact between the edge of the sleeve and the partition is provided only by the elasticity of the edge region of the sleeve and this results in very insufficient sealing at rest, in particular when the dispensed product is very viscous.
U.S. Pat. No. 4,124,150 discloses a dispensing assembly comprising a closure in the form of an elastically deformable member subjected to the action of a biasing member which tends to keep this closure applied against a seat with which it engages in order to ensure that the contact is sealed upon closure. The biasing member is formed by a kind of leaf spring which projects to the outside and is relatively bulky. Furthermore, such a system is composed of a number of pieces, incompatible with the economic constraints of the industrial environment.
European Patent Application EP 0,410,858 describes a device of the same type in which the closure means is subjected to the action of a rigid biasing member.
Most of these known devices, apart from the specific problems discussed above, require fitting operations which substantially affect the cost of the dispensing head.
U.S. Pat. No. 3,365,138 describes a dispensing head formed by an element made as a single piece, a first portion of which defines a chamber having orifices and a second portion of which is intended to be turned up over the first portion so as to close off the holes selectively. The two portions are formed from the same elastically deformable material, so as to allow it to be turned up, as mentioned above. Thus, there is an elastically deformable element which is bent back over a "body" which is also elastically deformable.
One of the problems associated with the design of the device described in that document stems from the fact that, upon opening, it exhibits a substantial inertia. Furthermore, making orifices in an elastically deformable body is made much more difficult, in particular when holes of small cross-section have to be made. This is because, due to the elastically deformable nature of the material, it is necessary to oversize the orifices, which is contrary to the goal of making small orifices. Finally, because of the relatively low resistance offered by the body, it is not possible to provide a very effective sealed closure.